Study on setup errors for different body carcinoma radiotherapy with image guidance in TOMO-HD

Objective The literature study the setup errors of head and neck, thoracic, abdominal and pelvic tumors by megavoltage fan-beam CT based image guidance in TOMO-HD to provide the margin enlarging from clinic target volume (CTV) to planning target volume (PTV) in treatment planning system of TOMO-HD. Methods 103 patients with head and neck (30 patients), thoracic (42 patients), abdominal and pelvic (31 patients) carcinoma were enrolled. Megavoltage fan-beam CT based image guidance in tomotherapy-HD was used to acquire CT scan before every treatment. The left-right (X), superior-inferior (Y), anterior-posterior (Z) and rotation (Fy) setup errors of patients can be obtained from the tomography image automatically restructured by the system. Calculating the systematic error and the random error in the three dimensions and check whether the setup data accord with the normal distribution or not, then acquire the data expand in the three directions. Results According to 2 593 fan-beam CT scans, the shift errors (µ ± s) in X, Y, Z and Fy (rotation) of three study group were [(−0.31 ± 2.16) mm, (1.09 ± 3.56) mm, (2.36 ± 2.27) mm, (0.29 ± 0.96)°] (head and neck tumor), [(−0.98 ± 2.95) mm, (0.45 ± 6.86) mm, (3.79 ± 2.47) mm, (0.18 ± 0.60)°] (thoracic cancer) and [(−0.86 ± 2.85) mm, (−1.59 ± 6.91) mm, (5.77 ± 2.40) mm, (0.20 ± 0.68)°] (abdominal and pelvic carcinoma). The systematic errors (Σ) and random errors (σ) in X, Y, Z dimensions of patients with head and neck, thoracic, abdominal and pelvic tumors were (1.06 mm and 1.84 mm), (1.93 mm and 3.43 mm), (2.41 mm and 2.71 mm), (1.10 mm and 2.56 mm), (3.79 mm and 5.46 mm), (1.38 mm and 1.99 mm) and (1.39 mm and 0.87 mm), (4.98 mm and 5.69 mm), (1.19 mm and 2.05 mm), respectively. Conclusion It is recommended as a reference for image guidance in TOMO-HD according to the frequency distribution of setup errors, for patients with head and neck, chest and abdominal and pelvic tumors, the maximum range of motion in three dimensions are (5.00, 5.00, 5.00) mm, (6,63, 17.25, 16.00) mm and (6.49, 16.24, 13.60) mm. 摘要： 目的 利用 TOMO-HD 螺旋加速器的 MV 级扇形束 CT 研宄头颈部、胸部、腹盆部肿瘤在放疗中的摆位误差, 为 PTV 边界的外扩提供数据支持。 方法 采用 TOMO-HD 螺旋断层系统分别对 30 例头颈部、42 例胸部和 31 例腹盆 部肿瘤患者每次放疗前行 MV 级扇形束 CT 扫描, 系统自动重建图像并与治疗计划 CT 图像进行配准, 获得患者左右 (X 轴)、头脚 (Y 轴)、腹背 (Z 轴)、沿Y轴方向的旋转 (Fy) 方向的摆位误差。计算出X、Y、Z方向的系统误差(Σ) 和随 机误差(σ)并对摆位误差进行正态性检验, 计算出 PTV 的各方向外扩边界。 结果 共行 2 593 次扫描, 头颈部、胸部、腹盆部患者在 X 轴、Y 轴、Z轴、Fy 方向 (沿 Y 轴方向的旋转) 的摆位误差 (µ ± s) 分别为 [(−0.31 ± 2.16)mm、(1.09 ± 3.56)mm、(2.36 ± 2.27)mm、(0.29 ± 0.96)°], [(−0.98 ± 2.95)mm、(−0.45 ± 6.86)mm、(3.79 ± 2.47)mm、(0.18 ± 0.60)°] 和 [(−0.86 ± 2.85)mm、(−1.59 ± 6.91)mm、(5.77 ± 2.40)mm、(0.20 ± 0.68)°]。头颈部、胸部、腹盆部患者在 X 轴、Y 轴、Z轴方向的系统误差(Σ)和随机误差(σ)分别为 (1.06 mm 和 1.84 mm)、(1.93 mm 和 3.43 mm)、(2.41 mm 和 2.71 mm)、(1.10 mm 和 2.56 mm)、(3.79 mm 和 5.46 mm)、(1.38 mm 和 1.99 mm) 和 (1.39 mm 和 0.87 mm)、(4.98 mm 和 5.69 mm)、(1.19 mm 和 2.05 mm)。 结论 根据不同部位的摆位误差频数分布, 头颈部、胸部、腹盆部不同 部位肿瘤患者的靶区在三维方向上最大运动范围参考值为 (5.00, 5.00, 5.00)mm, (6.63, 17.25, 16.00)mm 和 (6.49, 16.24,13.60)mm, 推荐以此作为图像引导参考。